[llvm] [GlobalIsel] Combine select to integer minmax. (PR #77213)

[Thorsten Schütt via llvm-commits]

tschuett wrote:

The combine is inspired by:
https://github.com/llvm/llvm-project/blob/83be8a74001904a63ed0cffa0cecc43649a7bb29/llvm/lib/Analysis/ValueTracking.cpp#L7726
The lower code in the legalizer has to pick one of two possible predicate values:
https://github.com/llvm/llvm-project/blob/83be8a74001904a63ed0cffa0cecc43649a7bb29/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp#L6939

I believe that is the cause for the changes in the `csel` instructions..

https://github.com/llvm/llvm-project/pull/77213